The sacrificial oxide etching of poly-Si cantilevers having high aspect ratios using supercritical CO₂

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• 作者：Ha Soo Hwang ; Jae Hyun Bae ; Jae Mok Jung ; Kwon Taek Lim
• 关键词：Etching ; Sacrificial oxide ; Poly-Si ; Supercritical carbon dioxide ; MEMS ; Cantilever
• 刊名：Microelectronic Engineering
• 出版年：2010
• 出版时间：November 2010
• 年：2010
• 卷：87
• 期：9
• 页码：1696-1700
• 全文大小：464 K

文摘

The aqueous etchants used in conventional wet etching for the micromachining of integrated circuits and MEMS devices often encumber the processes with a stiction problem. A dry etching method with anhydrous HF/pyridine in supercritical carbon dioxide (scCO₂) was developed to resolve the issue. A wafer composed of poly-Si cantilevers with various lengths and widths, and a sacrificial oxide P-TEOS were used to determine the longest cantilever that can be released without stiction. While stiction occurred over the 10 μm beams (gap to beam length, 1:20 aspect ratio) in wet etching, no stiction was observed after scCO₂ dry etching. SiF₄·2py residue was produced as a byproduct during the dry etching, which was attributed to the reaction between SiF₄ and pyridine. However, it could be removed completely from the wafer by subsequent flowing of a 10 wt. % bis(2-methoxyethyl)ether solution in scCO₂. Consequently, poly-Si cantilevers with high aspect ratios (1:150) were successfully released using this technique.